1. Field of the Invention
The present invention relates to an encoder.
2. Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 9-196705 proposes a method for removing a harmonic distortion (third harmonic component) of a modulated signal waveform in an encoder configured to receive light that has transmitted a scale grating and an index grating of a fixed unit, by converting an aperture width of the scale grating into a 2/3 pitch.
JP 9-196705 is disadvantageous because as the diffractive influence increases in the propagation from the scale grating to the index grating, the harmonic component is less likely to reduce.